1. Field of the Invention
The present invention relates to a vehicular wiper frame and a rubber blade mounted thereon, and more particularly, to a frame that can allow a rubber blade lying against a vehicular windshield to exert vertical pressure against the windshield. By maintaining the pressure against the windshield in a substantially vertical direction, the moment of a force generated between the wiping surface of the rubber blade and the surface of the windshield is minimized and a secure contact between the two surfaces is maintained.
2. Description of the Related Art
An automotive wiper is operated by a wiper motor through a mechanical linkage that moves the wiper arm back and forth in a predetermined arc. Disposed on the end of the wiper arm is a detachably mounted wiper frame to which a wiper blade made of rubber is attached.
Conventional wipers attached to wiper arms include a skeletal frame and a blade portion mounted on the frame and contacting a windshield to wipe it in a pendular movement.
Referring to FIG. 1, a conventional wiper 10 includes: a main frame 12 having an adapter 11 thereon for mounting the wiper arm 10; a first frame 16 symmetrically mounted on rivet joints 13 at either end of the main frame 12, and having a blade bracket 15 for evenly distributing load on the blade 14 and holding the blade 14 inserted therein; a second frame 17 symmetrically mounted on rivet joints 13 at either end of the first frame 16, and having blade brackets 15 on either end thereof for evenly distributing load on the blade 14 and holding the blade 14 inserted therein; a blade 14 having a rail portion 19 formed thereon along in which resilient tension springs 18 and 18a having a predetermined elasticity are inserted, the resilient tension springs applying a predetermined load furnished by the first and second frames 16 and 17 along the length of the blade 14 so that the blade 14 presses evenly against a windshield when wiping it; and a metallic tension spring 18 and 18a inserted along the length on either side of the blade 14 to support the load furnished by the first and second frames 16 and 17.
Here, in order for the main frame 12 to transmit the movement of the wiper arm 10 to an arcuate movement of the blade 14, the wiper arm 10, blade 14, and the tension springs 18 and 18a that provide resilience to the blade 14 converge at one point so that they move in unison according to the movement of the wiper arm 10. Also, the first and second frames 16 and 17 evenly distribute load furnished by the main frame 12, and, along with the main frame 12, are press-formed to have holes formed therein to facilitate water drainage and reduce weight.
The blade has a groove 20 (see FIG. 3) running lengthwise therealong for guiding the blade brackets 15 of the first and second frames 16 and 17, and a separate rail portion 19 for accommodating the tension springs 18 and 18a that provide resilience to the blade 14.
In the structure of this type of wiper, because the load on the blade is applied at certain points on the blade, it is unevenly distributed along the length of the blade. This unevenness causes premature wear of blade areas that are more compressed, while less compressed areas are prone to streak or overshoot the windshield glass underneath.
The wiper shown in FIGS. 4 and 5 does not have a main frame supporting a metal frame separately from a blade, but has tension springs inserted in the blade 14, over which a rubber cover 21 covers the unit.
That is, the rail portion 19 is formed along the lengths on either side of the blade 14, tension springs 18 and 18a are inserted into each rail portion, and a rubber cover 21 that functions as a spoiler is then inserted over the unit to conceal the tension springs 18 and 18a. 
The problem with the foresaid wiper is that the aggregate tension of the two tension springs 18 and 18a and the rubber cover 21 necessitate the wiper arm maintaining an increased load on the wiper for the wiper to be operationally effective, unduly stressing the mechanism. Also, this type of wiper is not interchangeable with existing wiper arms on vehicles that have a tension present for the previously mentioned multi-point-type wiper blade. Furthermore, because the wiper requires the rubber spoiler-cum-cover to complete the formation thereof, the latter item cannot be omitted.
Another conventional type of wiper, shown in FIGS. 6a and 6b, is formed with a separate spoiler 22 fitted at the top of the rubber blade that the tension springs are inserted into. This type of blade prevents vibration, while maintaining a secure and even contact with a windshield.
However, because this wiper structure has an adapter 11 and frame 12 disposed in a vertical axis (H) direction of the adapter 11, the frame 12 and the tension spring by themselves cannot function as a spoiler. Therefore a separately formed spoiler is required, complicating the overall structure, and creating the possibility of vibration or judder caused by the spoiler and wind noise when pressed against a windshield.
In another conventional type of wiper shown in FIG. 7, the upper portion of the rubber blade 50 has a head portion 52 defining a mounting slot 51 for mounting the blade to a frame 60. The mounting slot 51 of the head portion 52 is inclined at an offset angle θ1 according to the disposition of a frame 60, such that a normal line of a cross section of the mounting slot 51 is offset by a predetermined angle from a vertical axis of the rubber blade 50. The lower portion of the rubber blade 50 that contacts a windshield is a wiping portion 53, which is formed perpendicularly on the vertical axis.
Thus, even without a spoiler, lifting of the wiper blade can be prevented at high speeds.
However, although the rubber blade is structurally prevented from lifting without a separately installed spoiler, the blade is not disposed vertically on the glass, so that its clearing capability diminishes.
That is, when the wiper operates and moves across the surface of the glass about the pivoting pressure center of the motor, the blade does not continuously contact the surface of the windshield at a perpendicular angle, thus failing to impart adequate contact between the blade and the windshield.
FIG. 8 is a typically shaped rubber blade 50a that is formed symmetrically around a center of a pressing force (fs), so that despite the position to which the wiper arm moves, the blade maintains a vertical contact with the surface of the windshield.
The rubber blade 50 with the anti-lift characteristic shown in FIG. 7 is asymmetrical to the left and right of the pressing force (fs) from the wiper arm so that the wiper blade cannot maintain a vertical disposition to the windshield throughout the movement range of the wiper arm. That is, the angle of the pressing force imparted on the rubber blade by the wiper arm cannot maintain a vertical disposition with respect to the surface of the glass, so that the wiper's contact, wiping ability, secure disposition, etc. are insufficiently maintained.